Download 17-A Evolution Note Packet

Evolution of the eye: http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html
Definitions
1.Theory
a)an explanation of how and why
a specific natural phenomenon
occurs
b)A former hypothesis that has
been tested with repeated
experiments and observations
and found always to work
2.Law: a rule that describes, but
doesn’t explain, a pattern in nature
and predicts what will happen under
specific conditions
The History of the Universe
Vol. 1, Pg. 1:
Big Bang
Vol. 21:
Earth Forms
(4.5 bya)
Vol. 23:
Life on Earth
Vol. 29: Cambrian Era
Diversity Explosion
Vol. 30
Pg. 385: Dinos
Pg. 450: Humans
I. Evidence from the past
A. Fossil -- any trace or remains of an
organism that has been preserved
B. fossil record - information scientists
have gathered about past life
1. provides evidence about the history
of life on Earth
2. Shows how organisms have
changed over time
Applying the fossil record
Fossil Evidence of Evolution
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Fossil Evidence of Evolution (Cont.)
Whale “missing links”
8
Fossil Evidence of Evolution
Evolutionary change in body size and toe
reduction of horses
9
C.Fossil Types
1. Actual remains -- bones and shells
resist decay and may be preserved
(e.g. in ice, in La Brea tar pits)
The Iceman ~5,300 yrs old
La Brea tar pits
~25,000 yrs old
2. Amber - hardened resin (tree sap),
may contain trapped insects
3. Petrified remains - organic tissues
replaced with minerals
4. Mold - the shape of an organism
preserved in rock as a hollow form (like
an ice cube tray)
5. Cast - when a
mold fills with
minerals to
form a replica
of the original
form (like the
ice cubes)
6. Imprint - a shallow impression made in
mud which later hardens into rock,
usually plants and feathers
7. Transformed remains - organic
materials changed over time by high
heat & pressure = coal, oil, etc.
D.Age of fossils
1. Important to determine in order to
show change over time
2. Relative dating
• Examine the rock layers
• bottom = oldest, top = youngest
• Determine the order in which events
occurred
3. Absolute dating
• Radioactive dating
• Determine exact age
4. Index fossils - fossils that have been
found only in a narrow period of time
• E.g. trilobites only lived between 500600 million years ago
5. Geologic time scale - a timetable
that divides Earth’s history into eras
• Based on organisms living
through time
II.
Origins of Life
A. Biogenesis -- living things can
only come from other living things
B.Where did the
first living things
come from?
1. Miller & Urey: experimental evidence
that organic compounds can form from
simpler compounds present in Earth’s
early atmosphere
2. First cells:
a) fossil evidence of prokaryotes from
3.5 billion years ago
b) These photosynthetic cells produced
enough oxygen to create an
atmosphere that heterotrophic
eukaryotes could survive in
Stromatolite
3. Endosymbiont theory
a) Eurkaryotic & prokaryotic cells
shared a mutualistic relationship
b) Over time, prokaryotic cells
became organelles instead of
distinct cells
c) Mitochondria and chloroplasts
share many characteristics with
prokaryotes, and are thought to
have formed by endosymbiosis
III. Leading up to Darwin
A. Lamarck - first attempt to explain
how organisms change over time
1. change is made by what
organisms want or need
2. acquired traits = inheritable
(HE WAS WRONG!)
Lamarck’s theory of how giraffes’ long
necks evolved
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IV. Darwin’s Theory of Evolution
A. Traveled on the Beagle for 5 years
as the ship’s naturalist
1. Observed land & organisms
everywhere they went
2. Began to notice connections
between species
http://etext.library.adelaide.edu.au/d/darwin/charles/
3. Most famous for his observations of
Galapagos finches
a) Some islands much drier than others
b) Different islands had their own,
slightly different varieties of animals
c) Long after returning from his journey,
Darwin hypothesized that new
species could gradually appear much
like animal breeders can artificially
develop new species through
selective breeding
Similar for tortoises on
different islands…
“normal” tortoise
Saddleback allows tortoise to reach
higher leaves on drier islands
B. Explaining his observations: natural selection
1. Variation: individuals in a population differ
from one another
2. Heritability: variations are inherited from
parents
3. Overproduction: organisms produce more
offspring than can survive (survival of the
fittest)
4. Reproductive advantage: some variations
allow the organism that possesses them to
have more offspring – those variations
become more common and the population
changes over time
Darwin’s
theory for
how long
necks
evolved in
giraffes
36
Why are albinos rare?
Why does a peacock have a large tail?
V. Evidence from the living things
A. Homologous structures
1. Similar elements derived from a
common ancestor (Same
Structure- Different Function)
2. e.g. wings, fins & arms
3. divergent evolution: when a single
species evolves into several
different forms that live in different
ways
Homologous Structures in Animals
Homologous Structures in Plants
Divergent evolution
B.Analogous structures
1. Structures that serve the same function
but differ in development & structure
ancestor (Same Function- Different
Structure)
e.g. wings of bats, insects, & birds
2. Convergent evolution: organisms
living in similar environments, subject
to similar selection pressure, end up
evolving common features
Analogous Structures
Convergent
Evolution
C.Vestigial Structures
1. reduced form of a body part that would
be a functional structure in other
organisms (inherited from ancestors)
Vestigial structures
of a whale
• Examples of vestigial organs:
– Humans: Muscles for wiggling ears
– Humans: Appendix –Tailbone- “GooseBumps”
– Boa Constrictors:Hip bones and tiny hind legs
– Manatees: Fingernails on their fins
– Blind cave fish: Nonfunctional eyes
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D. Embryonic Similarities
1. Embryos of closely related species
have similar patterns of development
2. All vertebrates have tails & gill slits
as embryos -- even humans!
E. Comparative biochemistry
1. Species that share more DNA
sequences are more closely related
2. Comparisons can help us build a
cladogram (“family tree”) to show
how organisms are related
F. Adaptations
1. Beneficial variations that increase
chances for survival &
reproduction
2. Camouflage: blend in with
environment
3. Warning coloration: predators
learn to avoid species that are
toxic by recognizing patterns
4. Mimicry: copy the warning
patterns to avoid predators
http://www.pbs.org/wgbh/evolution/library/01/1/l_011_03.html
Camouflage
Coral Snake
Venomous
Milk Snake
The Australian hammer orchid has taken advantage of a mating ritual of the Thynnid wasp, which involves a female wasp waiting on
top of a branch or plant for a male to spot her. The hammer orchid's flower mimics the female wasp looking upward for a male flying
by, complete with a fake shiny head and furry body. The orchid even releases an enticing female wasp pheromone.
When the male wasp tries to mate with the dummy female, he fails, but the orchid succeeds in getting pollen on the wasp. He flies
away, only to be fooled again by another orchid pulling the same trick. In the process, the wasp transfers pollen from flower to flower.
Place a real female wasp next to the orchid mimic, and a male wasp will spot the real deal. For this reason, natural selection has
favored flowers that happen to bloom in the period when male wasps are flying but females are not out yet.
F. Adaptations (Continued)
5. Migration – Seasonal movement
in search of Food
6. Hibernation– Seasonal Slumber
needed for survival – Heart Rate
and breathing rates drop severely
VI. Modern Evolutionary Biology
A. Combines Darwin’s theories with new
information about genetics & population
biology
B. Hardy-Weinberg
1. Genetic equilibrium: allele frequencies
in a population remain stable from one
generation to the next
2. Evolution = equilibrium upset
3. punctuated equilibrium: pattern of
evolution in which long stable periods
are interrupted by brief periods of
rapid change
4.Five conditions must be met in order
to maintain genetic equilibrium:
• No mutation
• Large population
• Random mating
• No migration in or out of population
• No natural selection
C. Agents of Evolutionary Change
1. Mutation: A change in a cell’s
DNA
– Ultimate source of genetic variation
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2. Small population: Random changes called
genetic drift
a) founder effect –
When a few
individuals start a
population
b) bottleneck effect drastic reduction in
population, and gene
pool size
3. Nonrandom Mating: mating with specific
genotypes
a)
Sexual selection: changes in the frequency of a
trait based on the ability to attract a mate
•
•
Peacock tails
Antlers/male size
66
Agents of Evolutionary Change
4.
Gene flow: movement
from one population to
another
-Tends to make
populations more alike
67
5. Natural selection:
environmental conditions
determine which individuals
in a population produce the
most offspring
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a) Stabilizing selection: average
phenotype is favored
• birth weight in human babies
b.) Disruptive selection:
individuals at either
extreme favored over
average
• Northern water snakes in
different habitats
•
Oak Tree Forest with many
trees producing big
acorns and many trees
producing small acorns
c) Directional selection: an extreme
version of a trait is favored
• Industrial melanism
Directional selection:
• Bacterial resistance to antibiotics
C. Speciation
1. Occurs when a population
becomes isolated
2. Natural selection works on the two
populations independently, so
different traits evolve
3. Become so different that they
cannot produce fertile offspring
even if the populations are reunited
** Grand Canyon Squirrels
http://video.pbs.org/video/1790635347/
VIII.Human Origins
A. Anthropology: branch of science
dealing with the physical, cultural,
and social development of the human
species
B. Hominins: early human-like species
1. Split off from other apes between
8 and 5 mya
2. Many different species coexisted
3. Not clear which species were
direct ancestors of humans
4. Hominin fossils
a) Lucy: shows a mixture of human and
apelike traits – the “missing link”
b) Hominin characteristics:
• Bigger brains
• Thinner and flatter face
• Lengthened thumbs and flexible wrists
• Bipedal (Walk on 2 feet)
o Bowl-shaped pelvis
o S-shaped spine
o Shorter arms
o Foramen magnum at the base of the
skull
Primate and human skulls
C. The genus Homo
1. Homo habilis:
• 2.4 – 1.4 mya
• “handy man”, first to make and use
tools
2. Homo ergaster:
• 1.8 - 1.3 mya
• migrated out of Africa
3. Homo erectus:
• 1.5 million to 400,000 years ago
• used fire
4. Homo neanderthalensis:
• 200,000-30,000 years ago
• Larger brains than modern humans
• Heavily muscled
• Buried their dead
• Coexisted with modern humans, not
direct ancestor
5. Homo sapiens:
• Appeared 195,000 years ago
• Sophisticated tools
• Able to survive in a wide range of
environments
6. Out-of Africa hypothesis: modern humans
evolved once, if Africa, and have since
migrated to all parts of the world
• Chemical evidence: studies of human
DNA have shown that modern humans
have a common ancestor about
200,000 years ago